Step 1

To prepare cheese sauce: Melt butter in a medium saucepan over medium heat. Add flour and whisk constantly until thickened and just starting to turn light brown, 2 to 3 minutes. Slowly add milk, whisking constantly. Cook, stirring often, until the mixture is thick enough to coat the back of a spoon, 10 to 12 minutes. (Do not boil.) Remove from heat and, a handful at a time, whisk in Cheddar and Parmesan until smooth. Stir in 1/2 teaspoon salt. (Reserve 2 1/2 cups for another use.)

Step 2

Preheat oven to 400 degrees F. Coat a 9-inch (or similar size) baking dish with cooking spray.

Step 3

To prepare enchiladas: Heat avocado (or canola) oil in a large skillet over medium-high heat. Add beef, onion and bell pepper and cook, crumbling the beef with a wooden spoon, until it is no longer pink and the vegetables are tender, 5 to 8 minutes. Stir in corn, cumin, chili powder and garlic powder; cook, stirring occasionally, until the corn is heated through and the spices are fragrant, about 1 minute. Remove from heat.

Step 4

Stir green chiles into 1 1/2 cups of the warm cheese sauce. Arrange one-third of the tortilla wedges in the prepared baking dish, overlapping as necessary to fit. Top with half the beef mixture and 1/2 cup of the cheese sauce. Repeat with half the remaining tortillas, the remaining beef mixture and 1/2 cup of the cheese sauce. Top with the remaining tortillas, the remaining 1/2 cup cheese sauce and tomato. Bake until bubbling, about 15 minutes.

Step 5

Meanwhile, prepare dressing: Combine vinegar, water, sugar, mustard, garlic, basil, oregano, salt and pepper in a blender. Puree until smooth. With the motor running, slowly add oil and puree until creamy. (Measure out 2/3 cup and transfer the remaining dressing to a large mason jar; refrigerate for up to 1 week.)

Step 6

To prepare slaw & serve: Toss coleslaw mix with 1/4 cup cilantro and 2/3 cup dressing in a medium bowl. Top the casserole with the remaining 1/4 cup cilantro and cut into 4 servings. Serve with the slaw.